In conventional production of semiconductor devices, chips are die-bonded to a wiring board with a liquid thermosetting adhesive or a film thermosetting adhesive (die-bonding step), then wires are bonded (wire-bonding step), and the chips are encapsulated (encapsulating step) (FIG. 4, V to VII). When a chip 2 is mounted on a wiring board 4 via an uncured adhesive layer 3, voids 5 are often formed in the adhesive, or voids 6 may be produced in an interface between the adhesive and the chip or the wiring board (FIG. 4). Such voids do not disappear and remain after the die-bonding step (FIG. 4). In particular, the use of a liquid adhesive frequently results in voids in the adhesive, and the use of a film adhesive often results in voids in the interface due to insufficient adhesion and insufficient followability to unevenness of an adherend surface.
These voids can be an origin of package cracks in reliability evaluation of semiconductor devices, and therefore should be eliminated.
To address this problem, Patent Document 1 improves the followability to unevenness of a wiring board by reducing the viscosity of a liquid adhesive applied, or by reducing the elastic modulus of a film adhesive used in the die-bonding or optimizing die-bonding conditions.    Patent Document 1: WO 05/004216